The present invention relates generally to method and apparatus for adjusting vehicle wheel alignment and, more particularly, to method and apparatus for adjusting caster and camber in a vehicle steerable wheel suspension assembly.
Many utility vehicles such as trucks and four-wheel-drive vehicles have a front wheel suspension assembly which includes a fixed axle housing which pivotally supports a wheel knuckle through a pair of ball joints. The wheel knuckle supports a wheel spindle which, in turn, rotatably supports a vehicle wheel assembly.
A number of devices have been provided for adjusting the camber and/or caster of wheels supported by such suspension assemblies. Such adjustment devices are generally of two types: (1) wheel shim-type adjustment devices, or (2) bushing-type adjustment devices.
Plate-type adjustment devices generally comprise a tapered shim member which is interposed between the steering knuckle and spindle. The amount of shim taper and the orientation of the shim determine the amount of camber adjustment provided. Grove, U.S. Pat. No. 4,037,680, issued July 26, 1977, which is hereby specifically incorporated by reference for all that is disclosed therein, describes such a camber adjusting shim.
Bushing-type camber and/or caster adjustment devices are described in Ingalls et al., U.S. Pat. No. 4,252,338, issued Feb. 24, 1981; Ingalls, U.S. Pat. No. 4,400,007, issued Aug. 23, 1983; Ingalls et al., U.S. Pat. No. 4,420,272, issued Dec. 13, 1983; and Drotar et al., U.S. Pat. No. 4,509,772, issued Apr. 9, 1985, all of which are hereby specifically incorporated by reference for all that is disclosed therein. In bushing-type camber adjustment devices, a camber and/or caster adjustment bushing is mounted in a bore portion of an axle housing. The bushing member has a generally cylindrical shape and has a bore extending therethrough which is adapted to accept the shaft portion of the ball joint therein. The bore which extends through the bushing is positioned in noncoaxial relationship with the central longitudinal axis of the bushing. Camber and/or caster adjustment are provided by relative rotation of the bushing within the associated bore in the axle housing. Due to the noncoaxial alignment of the bushing bore with the bushing central longitudinal axis, rotation of the bushing causes relative shifting displacement in the lower end of the ball joint which is mounted in the associated wheel knuckle. Relative forward and rear shifting movement of the ball joint lower end portion produces a change in the "caster" of an associated wheel. Relative lateral shifting movement of the ball joint lower end portion produces camber adjustment.
In certain vehicles manufactured by the Ford Motor Company, locating lugs are positioned adjacent to a bushing mounting bore in an axle housing. Camber adjustment bushings are provided which have peripheral cutouts in head portions thereof. These bushings are adapted to be installed in an associated axle housing bore with the cutout portions thereof engaged with the locating lugs. Such bushings are adapted to be positioned in a first orientation for providing a positive camber setting and a second, 180.degree. rotated position for providing a negative camber setting. No incremental camber adjustments between these two positions may be provided. No caster adjustments are provided by such bushings. Generally, a plurality of such bushings are provided. A different camber adjustment is provided by each bushing, e.g. plus or minus 1/4 degree, plus or minus 1/2 degree, plus or minus 3/4 degree, etc. In order to adjust camber using such bushings, it is necessary to first install the bushing in either a positive or a negative camber adjustment position. Next, the associated ball joint shaft is mounted in the bushing and the camber of the wheel is measured. If the camber is incorrect, it is necessary to remove the ball joint, remove the bushing, and select another bushing. The next bushing is then installed and the process is thus repeated until a bushing having the correct amount of camber adjustment has been selected.
A bushing assembly described in Ingalls, U.S. Pat. No. 4,400,007, includes a bushing member, annular lock ring, and snap ring which enable multiple camber and caster adjustments to be provided in a Ford-type suspension system as described above, without removal of the bushing member from the axle housing bore. However, a problem with this bushing assembly is that the surface portions of the bushing and lock ring members have relatively complex configurations which add significantly to production costs. Another problem with the bushing assembly of U.S. Pat. No. 4,400,007 is that only a limited number of alignment settings are provided.